Organic recycling with a pipe-cross or tubular reactor

ABSTRACT

The invention is directed to a process for enhancing the plant nutrient value of relatively low analysis organic waste material (e.g. sewage sludge) involves treating the waste material with an acid and base in a pipe-cross,reactor or tubular to form a melt; spraying the melt onto a recycling bed of fines in a granulator and flashing off the water contained in the melt as steam; rolling the melt onto recycled fine particles in a granulator to form granulated particles; and drying these granulated particles in a to form an enhanced plant nutrient value composition (e.g. a fertilizer or soil conditioner having a greater NPK value than the original relatively low analysis organic waste material). The process further includes drawing off the fumes from the granulator, passing them through a dryer with the granulated particles, and subsequently oxidizing the fumes to eliminate volatile organic compounds and/or gaseous hydrocarbon pollutants be converting such into carbon dioxide and water vapor.

RELATED APPLICATIONS

The present application is a continuation of co-pending application Ser.No. 11/522,083, which is a divisional of application Ser. No.10/322,802.

BACKGROUND

1. Field of the Invention

This invention is directed to systems, devices and methods forconverting organic material into fertilizer. More specifically, theinvention relates to pipe-cross or tubular reactors that produce anenhanced plant nutrient value composition.

2. Description of the Background

The disposal of sewage sludge is a significant world-wide problem.Current methods of disposing of sewage sludge include incineration,direct land or ocean application, heating and drying the sludge forsterilization and then applying it to land, depositing it in a landfill,or granulating the sludge with a standard rotary granulator with heatingand drying being provided by exogenous heat sources (e.g. by burningpurchased fuel). While some of these methods result in a fertilizer,such fertilizers are of relatively low analysis with regard to theirplant nutrient value.

Methods of expressing a fertilizer's plant nutrient value involveidentifying the fertilizer's NPK value, wherein N relates to the amountof nitrogen, P relates to the amount of phosphorus (expressed asP.sub.2O.sub.5), and K relates to the amount of potassium (expressed asK.sub.2O). Thus, as reported in U.S. Pat. No. 3,050,383, sewage sludgewith a 2.5/2.5/0 value contains two and a half percent nitrogen, two anda half percent phosphorous as P.sub.2O.sub.5, and zero percent potassiumas K.sub.2O. Except as otherwise indicated by usage, all percentagevalues herein are weight-based percentages (i.e. w/w).

Fortunately, methods exist for enhancing the nutrient value ofrelatively low analysis organic waste material. For instance, in theaforementioned Wilson patent (the contents of which are entirelyincorporated herein by reference), a method is disclosed for treatingdried animal manure and sewage sludge with controlled amounts of anacid, such as sulfuric acid, phosphoric acid (or an equivalentphosphorous compound, the strength of which is expressed as phosphoricacid), or mixtures thereof, and an aqueous ammoniacal solution, such asaqueous ammonia or ammoniacal nitrogen salt-containing solutions andtumbling the resulting reaction mass to form fertilizer granules havingan upgraded or enhanced plant nutrient value.

Other methods of enhancing the plant nutrient value of relatively lowanalysis organic waste material with acids, bases, or mixtures thereofhave also been described (e.g. U.S. Pat. No. 4,743,287, U.S. DefensivePublication T955,002, Norton et al. (Feb. 1, 1977), U.S. Pat. No.5,466,273, U.S. Pat. No. 5,125,951, U.S. Pat. No. 5,118,337, U.S. Pat.No. 5,393,317, and U.S. Pat. No. 5,422,015.

Tubular reactors are known in the art for producing ammonia salts (e.g.U.S. Pat. No. 6,117,406, U.S. Pat. No. 2,902,342, U.S. Pat. No.2,755,176, and U.S. Pat. No. 2,568,901, the contents of which are herebyincorporated by reference). Exothermic reactions are carried out in thetubular reactors by reacting a base with an acid in the reactor tube.European Patent Publication 770,586A1 also discloses that tubularreactors may be used for the treatment of relatively low analysisorganic waste material. This European Patent Publication generallydescribes a process of treating such organic waste by introducing theorganic waste, ammonia, and an acid into a tubular reactor, carrying outan exothermic reaction, separating vapor from sludge, and then furtherprocessing the sludge.

A component typically associated with tubular reactors is apreneutralizer. The preneutralizer is typically used in conjunction withtubular reactors to effect partial neutralization of the acid prior toits introduction into the reactor. However, the use of a preneutralizerposes various disadvantages including difficulty in obtaining accuratecontrol of flow rates. Additionally, operating and equipment costsassociated with the use of a preneutralizer often represent asignificant expense.

A reactor similar to the tubular reactor is the pipe-cross reactor.Pipe-cross reactors similarly allow for an exothermic reaction to takeplace, but typically involve the introduction of one or two differentacid solutions for reaction with a base in a method to thoroughly mixthe reagents. This is an important feature of pipe-cross reactors as iteliminates the need for a preneutralizer. At the first stage of thecross pipe reactor, the base and/or scrubber water and organic materialsolution are premixed. At the second step, pipe-cross reactors areformed with up to two acid inlets configured such that the acidsolutions are introduced perpendicular to the pipe cross reactor assubstantially opposing streams. The perpendicular entry and opposingstreams allow for thorough mixing of the acids within the reactor, thuseliminating the need for extraneous equipment such as a preneutralizer.

Pipe-cross reactors are well-known and have been used in the past toproduce granular NPKS fertilizers from liquid chemicals (e.g. EnergyEfficient Fertilizer Production with the Pipe-Cross Reactor (U.S. Dept.of Energy, 1982) (a pipe-cross reactor fit into the granulator drum of aconventional ammoniation-granulation system); Achom et al., “OptimizingUse of Energy in the Production of Granular Ammonium PhosphateFertilizer” (1982 Technical Conference of ISMA, Pallini Beach, Greece);British Sulfur Corp. Ltd., “TVA modifies its pipe reactor for increasedversatility”, Phosphorus & Potassium, No. 90, pp. 25-30 (1977); Achom etal., “Efficient Use of Energy in Production of Granular and FluidAmmonium Phosphate Fertilizers” (1982 Fertilization Association of IndiaSeminar, New Dehli, India), Salladay et al. “Commercialization of theTVA Pipe-Cross Reactor in Regional NPKS and DAP Granulation Plants inthe United States” (1980 Fertilization Association of India Seminar, NewDehli, India); U.S. Pat. No. 4,619,684; U.S. Pat. No. 4,377,406; U.S.Pat. No. 4,134,750; U.S. Defensive Publication T969,002 (Apr. 4, 1978)to Norton et al.; and Salladay et al., “Status of NPKSAmmmoniation-Granulation Plants and TVA Pipe-Cross Reactor” (1980Fertilizer Industry Round Table, Atlanta, Ga., US)). More recently,pipe-cross reactors have been successfully used to enhance the plantnutrient value of relatively low analysis organic waste material (e.g.U.S. Pat. Nos. 5,984,992 and 6,159,263, the entirety of both of which isincorporated by reference herein).

One potential drawback of exothermically treating relatively lowanalysis organic waste material with reactors, such as a pipe crossreactor or tubular reactor, is the potential for exhausting noxiousodors during the process. The use of cross-pipe reactors for treatingsuch waste has helped to reduce the odors typically associated with thetreatment thereof. However, a need exists to provide greater assurancethat such potential odors are eliminated, or at least reduced beyondcurrent emission levels.

Additionally, a continued desire exists to improve the efficiency ofsludge treatment, both in terms of capital expenditure as well as inoperating costs.

There is a need in the art for relatively simple and efficient processesfor processing relatively low analysis organic waste material to anenhanced plant nutrient value composition without substantial emissionof noxious odors. Preferably, such processes would produce products thatwere sized and shaped to be spread by commercially available commercialspreaders.

SUMMARY OF THE INVENTION

The present invention surprisingly overcomes the problems anddisadvantages associated with current strategies and designs, andprovides improved systems and methods for treating organic material,namely sludge.

One embodiment of the invention is directed to methods for treatingrelatively low analysis organic waste material having a solids contentof at least approximately five percent or greater to form an enhancedplant nutrient value composition. These methods comprise mixing therelatively low analysis organic waste material with scrubber water toform a slurry which is capable of being pumped. The slurry is pumpedinto a pipe-cross reactor or tubular reactor for reaction with a baseand acid, to form a melt. The melt is sprayed onto a recycling bed offines in a granulator and liquid is flashed off of the melt in the formof steam. The melt is rolled onto fine particles in the granulator toform granulated particles further reacted with a base to complete theproduct formation, and subsequently dried in a dryer to reduce themoisture content of the granulated particles. Fumes created during theprocess, such as the flashed off steam, which may also containparticulates and ammonia, are oxidized to destroy gaseous hydrocarbonpollutants contained therein.

Another embodiment of the invention is directed to devices and systemsfor treating relatively low analysis organic waste material having asolids content of at least approximately five percent in forming anenhanced plant nutrient value composition. The system comprises apipe-cross reactor or tubular reactor which is configured to receive aslurry, a base, and an acid therein. The reactor is configured to givethorough mixing and retention time so as to allow substantial completionof a reaction between the components introduced therein and form a meltfrom such components while flowing through the reactor. Substantialcompletion means that substantially most of the heat of mixing isgenerated by the mixing step. Preferably at least 50%, 60%, 75%, 85%,90% or even 95% of the total mixing heat produced by the exothermic stepis generated. A granulator, positioned to receive the melt from anoutlet of the reactor, is configured to further react the melt with thebase reagent to complete product formation and to mix fine particleswith the melt to form granulated particles. A dryer receives thegranulated particles from the granulator and reduces the moisturecontent thereof resulting in substantially dried granulated particles. Agranule separator receives the dried granulated particles and separatesthem into fines, product, and oversized particles. The system may alsocomprise an oxidizer that receives fumes formed during the reaction,granulation, and drying processes. The oxidizer removes gaseoushydrocarbon pollutants from the fumes prior to their exhaust.

Another embodiment of the invention is directed to methods for treatingrelatively low analysis organic waste having a solids content of atleast approximately five percent to form an enhanced plant nutrientvalue composition. These methods comprise mixing the relatively lowanalysis organic waste material with scrubber water to form a slurrywhich is capable of being pumped. The slurry is pumped into a pipe-crossreactor or reactor for reaction with a base, and acids to form a melt.The melt is sprayed onto a recycling be of fines in a granulator andliquid is flashed off of the melt in to form of steam. The melt isrolled onto fine (smaller) particles in the granulator to formgranulated (larger) particles and then further reacted with the basereagent to complete product formation and subsequently dried in a dryerto reduce the moisture content thereof, resulting in an enhanced plantnutrient valued composition in the form of dried granulated particles.The granulated particles are conveyed to a dryer along with the steamflashed off during the reaction and granulating processes. Thegranulated particles are then dried to reduce the moisture contentthereof to form dried granulated particles which comprise an enhancedplant nutrient value composition.

Another embodiment of the invention is directed to systems for treatingrelatively low analysis organic waste material having a solids contentof at least approximately five percent in forming an enhanced plantnutrient value composition. The system comprises a pipe-cross reactor ortubular reactor for receiving a slurry, a base, and an acid therein. Thereactor is configured to give thorough mixing and adequate retentiontime so as to allow substantial completion of a reaction between thecomponents introduced therein and form a melt from such components whileflowing through the pipe-cross reactor. A granulator, positioned toreceive the melt from an outlet of the reactor, is configured to furtherreact the melt with the base reagent to complete product formation andto mix fine particles with the melt to form granulated particles. Adryer receives the granulated particles from the granulator and reducesthe moisture content thereof resulting in substantially dried granulatedparticles. The dryer also receives the flashed-off steam and fumesformed during the reaction and granulation processes. A granuleseparator receives the dried granulated particles and separates theminto fines, product, and oversized particles.

Other embodiments and advantages of the invention are set forth, inpart, in the following description and, in part, may be obvious fromthis description, or may be learned from the practice of the invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1—A process flow diagram of one embodiment of the invention.

FIG. 2—A stylized view of a pipe-cross reactor.

FIG. 3—A partially cut away, perspective view of a pipe-cross reactor ina rotary ammoniator-granulator.

FIG. 4—A stylized end view of a rotating bed of material in agranulator.

FIG. 5—A side view of an orifice plate utilized with a pipe-crossreactor.

DESCRIPTION OF THE INVENTION

As embodied and broadly described herein, the present invention isdirected to systems and methods for treating organic material. Morespecifically, the present invention relates to systems and methods fortreating sludge and converting sludge into fertilizer.

As depicted in FIG. 1, a process for enhancing the plant nutrient valueof organic waste material generally involves mixing the organic wastematerial with water in an agitation tank or sludge slurry tank 10 toform a slurry. The water used in making the slurry may desirably includescrubber Water from the hereinafter described scrubber 38, which maycomprise waste acid. The slurry is mixed at a sufficient concentrationand consistency such that it will, preferably, process the organic wastematerial as quickly as possible, but will not clog or block a reactorduring operation. A preferred reactor is a pipe-cross reactor 12, but atubular reactor might alternatively be used, or even used, in a system,in conjunction with a pipe cross reactor. The particular slurryconcentrations and consistencies will depend, to some extent, on thesize and amount of insoluble particulate material contained in theparticular organic waste material and the size and length of the reactorcomponents. However, as delivered to the pipe-cross reactor, the slurrygenerally has a solids content of at least about five percent andpossibly as high as about 35%. Preferably, the solids content of theslurry is from about 10% to 27%.

As depicted in FIG. 1, the slurry is pumped from the agitation tank 10to a pipe-cross reactor 12 for an exothermic reaction with, for example,a base such as ammonia and an acid or acids such as sulfuric acid,phosphoric acid, and mixtures thereof, with or without extra water toform a melt.

Amounts of acid and base used in the exothermic process can bedetermined by one of skill in the art. However, for guidance in theneutralization of ammonia, approximately one mole of sulfuric acid, ortwo moles of phosphoric compounds expressed as phosphoric acid, is usedfor each two moles of ammonia. Concerning the concentration ofphosphoric acid, typical molar ratios of N:P in the pipe-cross reactorare between 0.4:1 to 0.7:1, preferably 0.55 to 0.65:1, concerning theconcentration of sulfuric acid, typical molar ratios of N:S in the pipecross reactor are between 0.5:1 and 0.8:1 preferably 0:65:1 to 0.72:1.The molar amount of nitrogen should take into consideration not only theamount of ammonia being added but the typical amount of ammoniacalnitrogen contained in the particular organic waste material.

Other acids which may be used with the invention comprise nitric acid,acetic acid, citric acid and mixtures thereof, all of which are wellknow to those skilled in the art (e.g, nitric acid and an ammoniacompound which might form ammonium nitrate in the presence of organicmaterials which is explosive). Whatever the acid or acids chosen, thestrength of one of the acids used in the process will preferably beequivalent to 90% sulfuric acid (e.g. 93 to 100 percent sulfuric acid).

As depicted in FIG. 2, the pipe-cross reactor 12 is preferably providedwith two cross pipes 26, 28 to receive sulfuric acid (at a rate of about17.2 to 25.8 gpm) and phosphoric acid (at a rate of from about 5.2 to7.8 gpm). A third pipe 30 incorporates the ammonia into the center ofthe reactor. The length of this pipe 30 is desirably at least twenty tothirty inches to ensure adequate mixing. A third cross pipe 32incorporates the slurry and additional water into the mixing chamber.Positioned between the third cross pipe 32 and the first and secondcross pipes 26 and 28 is an orifice plate 33 which is utilized tointroduce turbulence into the flow of the slurry ensuring even greatermixing.

A typical pipe-cross reactor for use with the invention has a diameterof about three to ten inches, is from about seven to about fifty feetlong, and terminates in, for example, a two to eight inch discharge pipe(or a slot of equivalent cross-sectional area), preferably with astainless steel insert or TEFLON™ lining. The discharge pipe preferablydischarges into a standard rotating drum granulator 14, and ispreferably made of a steel pipe (e.g. HASTELLOY C-276 or 316L stainlesssteel (with HASTELLOY C or B for the reaction tube)). A TEFLON™,ceramic, or other corrosion-resistant lining may also be used in thepipe-cross reactor. The temperature is preferably maintained below204.degree. C. (400.degree. F.).

The orifice plate 33, as shown in FIG. 5, includes a plate formed from amaterial similar to the pipe-cross reactor 12 and includes an orifice 35or aperture which exhibits a smaller diameter than that of thepipe-cross reactor 12. Thus, for example, a pipe-cross reactor having a(6) inch diameter would employ an orifice plate 33 having an orifice 35which exhibited a diameter less than inches, for example inches. Indetermining the size of the orifice 35, various parameters may beconsidered including flow rates of the slurry, acids and base, as wellas the solid content of the slurry. Thus, the size of the orifice 35 maybe changed for a given pipe-cross reactor 12 if the any processparameters are altered.

Although FIG. 5 shows use of a circular orifice plate, it wassurprisingly discovered that adding a protuberance generally to increaseturbulence upstream of the two pipe cross reactor provides greater heatrecovery. In other embodiments, the turbulence is created through use ofa protuberance, such as a bump, multiple bumps in series or parallelwith respect to the flow stream, one or more wires, input of pressurizedgas such as air, use of a sonic vibrator or vibrating wall at thisposition. For example, two, three, four, five, six, seven, eight or moreequally spaced bumps that each protrude into the space towards the lumenmiddle, by, for example, 0.02, 0.05, 0.1, 0.2, or 0.3 times the diameterat that point may be used to create turbulence. In an embodiment a bumpis an annular thickening that forms a constriction within the pipe. Asonic vibrator (for example such as that offered by Advanced Sonics,also may be used. A restriction, as shown in FIGS. 2 and 5, does nothave to be round but can be another cross sectional shape, such as oval,square or irregular. An oval share is desirable, particularly with thenarrow ends pointed to the cross pipes such that the larger oval axisextends across a line connecting the two cross pipe openings. In anotherembodiment the short axis of the oval extends across a line connectingthe two cross pipes. The oval shape with long matching axis provides aturbulence that more closely matches the incoming flows from theperpendicular cross reactors and is particularly desired whenperpendicular cross pipe reactors as shown in FIG. 2 are used.

The optimum placement of the protuberance(s) in many embodiments isbetween 0.1 to 3 flow stream diameters upstream of the average positionof the cross reactor outlets (i.e. mean of the cross reactor outlets,which may be staggered down the length of the flow stream). Morepreferably the protuberances are located between 0.3 to 1.5 diametersahead of the cross pipe reactors. Optimum placement will vary dependingon the flow rate. For a very high flow rate the protuberance(s) shouldbe set further away or the degree of protuberance into the flow pathshould be limited. This embodiment may be carried out by an adjustableannular ring or adjustable bumps that provide the ability to control thedistance away and the degree of flow path entry of the protuberance. Anannular ring may be adjusted for opening size and may be mounted atalternative locations, for example. Multiple sonic vibrators, if usedmay be placed at different locations and individually switched toaccommodate slower (vibrate closer to the cross pipes) or faster(further away location) flow rate and/or lowered viscosity.

Adjustment of the cross pipe reactor itself may be optimized for a givenviscosity and flow rate. In many embodiments the cross reactor pipesadvantageously are exactly opposite each other, as shown in FIG. 2. Thisplacement is desirable when adding comparable viscosity fluids atcomparable flow rates. Also desirable, is the use of multiple (3 or 4,or more) cross pipes. For example, a four way (four perpendicular pipes)that administers two materials each through two opposing sides, may beused if the viscosity is low enough. Multiple cross reactor pipes may beswitched to accommodate changes in viscosity and/or flow rate. Forexample a less viscous material or higher flow rate system may benefitby using one or more cross reactor inlets that are further away (moredownstream) with respect to the protuberance(s) and that can be openedand closed. Other combinations may be optimized upon routinecalibration, by changing the flow, and/or type of sludge material and/ora reagent and then monitoring for heat recovery by measuring temperaturedownstream at one or more points. By providing adjustableprotuberance(s), and/or cross pipe placements, and/or flow ratesoptimized heat recovery may be obtained.

Yet another embodiment provides an automatic system that constantlymonitors temperature of mixed material at some point downstream of thecross pipe reactor and adjusts protuberance positioning, flow rate ofsludge, flow rate of base, flow rate of added water, flow rate of one ormore acids, and switching of cross reactor outlets for optimum effect.In a desirable embodiment flow rate of base, and/or dilution waterand/or an acid and/or a second acid and/or sludge is adjusted up or downto obtain a higher temperature. In another embodiment a switch selectsbetween two or more cross pipes to obtain a more desirable temperature.In yet another embodiment some of the released heat is transferred in acontrollable way back to an input stream to obtain a more desirableviscosity for adequate mixing. A control system may adjust heat transferup or down depending on the heat recovered, or depending on anothermonitored variable, such as back pressure to the sludge pump(s) or backpressure measured at a pipe-cross reactor gauge.

Without wishing to be bound by any one theory of this embodiment of theinvention, it is thought that the use of a protuberance such as anorifice plate allows greater mixing of the slurry by inducing a zone ofturbulence downstream of the orifice plate 33 and generally in thevicinity of the first and second cross pipes 26 and 28. The increasedturbulence generated in many cases increases heat production as measuredas a higher melt temperature. The temperature also can be measured at ordownstream of the last cross pipe addition of reagent, such as forexample, 1 or 2 pipe diameters further downstream of the last crosspipe. It has been observed that use of an orifice plate has effected anincrease of heat recovery, as much as approximately 30%, over similarpipe-cross reactors lacking an orifice plate. An orifice plate 33 may bechanged for another orifice plate exhibiting a different diameterorifice 35 if desired.

Referring to FIG. 2, ammonia is introduced into the representativesystem depicted here at a rate of from about 4.3 gpm. Organic wastematerial (e.g. sewage sludge) and water are incorporated at a rate offrom about 30 to about 40 gpm of slurry. The pipe-cross reactor shownhere typically operates at a gage pressure of between fifteen and sixtypsig.

A hot melt discharges from the pipe-cross reactor 12 into the granulator14, while water flashes from the reactor product as it issues into thegranulator 14. Steam is generated by the exothermic reaction conductedwithin the pipe-cross reactor 12.

A preferred granulator (e.g. an ammoniator-granulator), depicted inFIGS. 3 and 4, is a two to four meter diameter rotating drum granulatorhaving a length of from about five to about nine meters. As shown inFIG. 3, the pipe-cross reactor 12 is oriented vertically and includes anumber of 90 transitions or bends prior to entering the granulator 14.The shown position of the pipe-cross reactor 12 is preferred as itprovides greater mixing capabilities. However, satisfactory results maybe achieved with the pipe-cross reactor 12 oriented horizontally withoutany transitions or bends (e.g. U.S. Pat. Nos. 5,984,992 and 6,159,263).

In the depicted process, the granulator 14 includes an ammonia sparger20 operably positioned within the granulator 14 for the addition ofammonia to the melt to complete the reaction of acid and base for thefinal product. The melt is rolled onto recycled fine particles withinthe granulator 14 to form granulated particles, thus causing thegranulated particles to grow to a desired size. Afterwards, as depictedin FIG. 1, these granulated particles are passed into a rotary dryer 16for a sufficient amount of time to reduce their moisture content, thusforming a fertilizer having an enhanced plant nutrient value. The vaporsformed during the reaction of the slurry with the acid and base (e.g.the flashed off steam) are also collected and conveyed into the rotarydryer 16 for increasing the dew point vapors so as not to condense inthe plant equipment.

Passing such vapors directly into the dryer 16 is an alternative processas compared to that of U.S. Pat. Nos. 5,984,992 and 6,159,263. Previousprocesses associated with pipe-cross reactors have typically separatedthe granulated particles from the vapor for independent processing priorto the drying of the granulated particles. The presently depictedprocess eliminates the need for additional particulate separationequipment and processing of the air and ultimately results in a simplerand more efficient process.

A preferred dryer for use with the invention is a two to four meterdiameter rotating drum dryer having a length of from about seventeen toabout thirty three meters, and having a heating capacity of 30 to 70million BTU/hour, with a lump crusher at the discharge end.

The process further includes passing the dried granulated particles to agranule separation apparatus, such as a screen 18, and separating thedried granulated material into fines, product and oversized material.Oversized material is reduced in size to be incorporated, as a fine,back into the process. The fines are returned to the granulator 14(along with potash or any micronutrients required for the desired finalproduct analysis) for incorporation into the process.

During the process, fumes, which may contain ammonia, particulates, andwater vapor above its dew point, are collected from the dryer 16 andpassed through particulate separating equipment, such as a dust cyclone34. The dust cyclone 34 removes a portion of the particulates from theair and recycles these particulates (e.g. dust) with the fines andground material. The resultant fumes leave the dust cyclone 34 and areprocessed through additional particulate separating equipment, such as abaghouse filter 36. The baghouse filter serves to remove an additionalamount of particulates, particularly particulates which exhibit asmaller size than those removed by the dust cyclone 34. Particulatesremoved from the baghouse filter 36 are similarly recycled with thefines and ground material for use in the granulator 14.

The fumes leaving the baghouse filter 36 are subsequently processedthrough a scrubber 38, such as a venturi scrubber or packed bedscrubber, which includes water separation chambers for collectingammonia fumes and small dust particles. The invention uses low pH waterin the scrubber 38 to collect unreacted ammonia vapors escaping thegranulator 14. In one embodiment, small amounts of sulfuric orphosphoric acid are added to the scrubber 38 to maintain a low pH (e.g.2 to 3) for proper ammonia vapor scrubbing.

The process further includes oxidizing the air exiting the scrubber,such as in a regenerative thermal oxidizer (RTO) 40. The RTO 40 is usedto destroy volatile organic compounds (VOCs) and other gaseoushydrocarbon pollutants that would otherwise be released into theatmosphere. The RTO 40 destroys such VOCs and hydrocarbon fumes througha process of high temperature thermal oxidation, converting the VOCs andfumes to carbon dioxide and water vapor. The oxidation of the airfurther serves to substantially eliminate any noxious odors that wouldotherwise be exhausted into the atmosphere. Energy released from theoxidation process is recycled to reduce operating costs.

Air is drawn from the RTO 40 and exhausted into the atmosphere through astack 42. The process may advantageously include using heat from theexhaust in the stack 42 to preheat the base (e.g. ammonia) prior to itsintroduction into the pipe-cross reactor 12 and/or the granulator 14 viathe sparger 20.

Another aspect of the ventilation for the depicted process includescollecting air from the screens 18. The process contemplates twooptions, both of which involve particulate removal and recycling of bothparticulates and air. The first option includes processing the airthrough a dust cyclone 34 and recycling both the particulates and theair back to the granulator 14. The second option includes utilizing thedust cyclone 34, but further includes processing the air through abaghouse filter 36, again collecting the particulates for recycling inthe granulator. The air leaving the baghouse filter 36 is advanced tothe dryer 16 instead of the granulator 14.

Other aspects of a ventilation system for use with the inventionpreferably include fans for moving the air to and from the variousprocessing stages described above herein. Volume of air moved isdetermined by the amount of moisture to be removed (above dew point) andthe melting point or disassociation temperature of the fertilizerproduct.

NPK fertilizers preferably include the micronutrients iron and zinc. Ina preferred embodiment, spent acid from a hot dip galvanizing or steelpickling process is used to maintain the low pH of the scrubber water.These spent acids commonly are sulfuric acid of five to ten percentstrength, containing three to eight percent iron. Galvanizing spent acidcontains three to eight percent zinc along with iron. The iron and zincare fed with the ammonia-laden scrubber water from scrubbing to thesludge slurry tank and on to the pipe-cross reactor for incorporation asiron and zinc micronutrients in the final NPK fertilizer. In the case ofspent sulfuric acid, the sulfur also becomes a nutrient in the resultingfertilizer, since it reacts in the pipe-cross reactor to form ammoniumsulfate.

Other micronutrients or additional ingredients may be incorporated intothe resulting fertilizer by adding them with a weigh feeder as a drysolid to the fines recycle stream. Micronutrients or additionalingredients include lime, dolomite, calcite, hydrobiotite, gypsum,phosphates (e.g. rock phosphate or ammonium phosphate), potash, urea,soil clays, calcium peroxide, ammonium nitrate, vermiculite, humic acid,and trace minerals such as iron, manganese, magnesium, boron, copper,and zinc.

Although the invention has been most particularly described for theprocessing of municipal sewage sludge, the inventive process may also beused to enhance the plant nutrient value of other relatively lowanalysis organic waste material such as poultry manure, food processingwastes, wastes from paper manufacturing, swine manure sludge, mixturesthereof, and the like. In such a case, the particular relatively lowanalysis organic waste material is substituted for the sewage sludge inthe process, and the process parameters are accordingly modified.

The following examples are offered to illustrate embodiments of thepresent invention, but should not be viewed as limiting the scope of theinvention.

Examples Example 1

In an agitation tank, 6700 kilograms/hour (7.4 tons/hour) of sewagesludge were mixed with 37 liters per minute (ten gallons/minute (gpm))of scrubber water to form a slurry. The slurry was of such a consistency(a solids content varying between 10% and 27%) that it can bepumped-with a positive displacement pump or other suitable pump to apipe-cross reactor equipped to receive ammonia, sulfuric acid,phosphoric acid, sewage sludge, and water. The pipe-cross reactor had adiameter of approximately four inches and was forty feet long. Thepipe-cross reactor terminated in a rotating drum granulator. Therotating drum granulator was six feet in diameter and twenty feet long.

The slurry was added to the pipe-cross reactor and reacted with 8.6 gpm99.5% ammonia, 8.6 gpm sulfuric acid (93%), and 2.6 gpm phosphoric acid(54% P.sub.2O.sub.5). The temperature of the pipe-cross reactor (due tothe exothermic reaction between the acid and the base) was maintained atabout 149.degree. C. (300.degree. F.) with moisture in the sludge. Thistemperature (above minimum sterilization temperature) acts to killSalmonella, E. coli, and other pathogens which may be found in theslurry. This temperature also acts to deodorize the material somewhat.

The resulting melt from the pipe-cross reactor is sprayed onto arecycling bed of fines, along with 2000 pounds of added potassiumchloride (60% K.sub.2O) while the water contained in the melt flashedoff as steam. An ammonia sparger is provided in the granulator to addsmall amounts of ammonia to the granulation mixture for reactioncompletion and final hardening of granules.

Operating the pipe-cross reactor in such a manner incorporatedapproximately 14.8 tons per hour of 20% solid sewage sludge at a ten tonper hour production rate.

Granulated material exits the granulator at about 93.degree. C.(200.degree. F.) and at about a five to fifteen percent moisture contentinto a rotary dryer. The rotary dryer was approximately two meters indiameter and has a length of about twenty meters. It has a heatingcapacity of 30 million BTU/hour and is associated with a lump crusher orlump breaker at the discharge end. The moisture in the material wasreduced to less than three percent by heated forced air in the dryer.

Materials exiting the rotary dryer were run through the lump crusher toreduce oversized material to less than one inch in size.

Screens are used to separate the material into (a) fines, (b) productand (c) oversized material. Fines are returned to the granulator.Product went to a two meter diameter, twenty meter long cooler and thenon to storage, while the oversized material is passed through a grindingmill and reduced to fines for recycling to the granulator. About twotons (1800 kg) of fine material per ton of product were required in therecycle stream.

Fumes from the granulator containing steam, ammonia and particulate werecollected by maintaining a negative pressure inside the granulator witha fan pulling the fumes into the rotary dryer to reduce the moisturecontent thereof. The air was drawn from the granulator at a rate of20,000 cubic feet per minute (cfm) at a temperature of 92.degree. C.(198.degree. F.) and at 100% relative humidity. This is roughlyequivalent to conveying 34,200 pounds per hour (lbs/hr) of water and 296pounds per minute (lbs/min) of dry air.

The air from the rotary dryer was directed to a dust cyclone, a baghousefilter, and then a scrubber. Air was drawn from the dryer at a rate of70,000 cfm at 45% relative humidity. The air leaving the dryer had a drybulb temperature of approximately 93.degree. C. (200.degree. F.) and awet bulb temperature of 74.degree. C. (165.degree. F.). This is roughlyequivalent of conveying 56,100 lbs/hr water and 2,711 lbs/min of dryair. Air entering the scrubber is scrubbed with low pH water (water at apH lowered by the addition of spent acid from a hot dip galvanizingprocess). If galvanizing acid is unavailable, the pH may be controlledwith phosphoric or sulfuric acid. The low pH water collects ammoniavapor present in the fumes, as well as dust particles.

Air was directed from the scrubber to a regenerative thermal oxidizer ata rate of 67,100 cfm at a temperature of 165.degree. F. and at 100%relative humidity. Oxidized air was then drawn from the regenerativethermal oxidizer and is exhausted through a stack approximately onehundred (100) feet tall at a temperature of 93.degree. C. (200.degree.F.).

Dust-laden air is collected from the grinding mills and screens by a fanmaintaining negative pressure on the equipment. The air is pulledthrough a cyclone system that removes about 97% of the dust. From thecyclones, the air was passed back to the rotary granulator and the dustadded to the recycled fines.

The resulting fertilizer had an NPK value of 12-3-6 (12% nitrogen, 3%phosphate, and 6% potash). It was also homogenous and properly sized forstandard application equipment.

Example 2

The process of Example I is repeated in a tubular reactor rather than apipe cross reactor. In an agitation tank, 6700 kilograms/hour (7.4tons/hour) of sewage sludge are mixed with 37 liters per minute (tengallons/minute (gpm)) of scrubber water to form a slurry. The slurry isof such a consistency that it can be pumped with a positive displacementpump or other suitable pump to a tubular reactor equipped to receiveammonia, sulfuric acid, phosphoric acid, sewage sludge, and water. Thetubular reactor preferably has a diameter of approximately 1.5 to 30 cmand a length of 2 to 10 meters, preferably 5 to 8 meters. The reactorterminates in a rotating drum granulator. The rotating drum granulatoris six feet in diameter and twenty feet long.

The slurry is added to the reactor and reacted with 8.6 gpm 99.5%ammonia, and an acid solution containing 8.6 gpm sulfuric acid (93%) and2.6 gpm phosphoric acid (54% P.sub.2O.sub.5). The temperature of thereactor (due to the exothermic reaction between the acid solution andthe base) is maintained at about 149.degree. C. (300.degree. F.) withmoisture in the sludge.

The resulting melt from the reactor is sprayed onto a recycling bed offines, along with 2000 pounds of added potassium chloride (60% K.sub.2O)while the water contained in the melt flashes off as steam. An ammoniasparger is provided in the granulator to add small amounts of ammonia tothe granulation mixture for reaction completion and final hardening ofthe granules.

Granulated material exits the granulator at about with a moisturecontent into a rotary dryer. The rotary dryer is approximately twometers in diameter and has a length of about twenty meters. It has aheating capacity of 30 million BTU/hour and is associated with a lumpcrusher or lump breaker at the discharge end. The moisture in thematerial is reduced to less than three percent by heated forced air inthe dryer.

Materials exiting the rotary dryer are run through the lump crusher toreduce oversized material to less than one inch in size.

Screens are used to separate the material into (a) fines, (b) productand (c) oversized material. Fines are returned to the granulator.Product goes to a two meter diameter, twenty meter long cooler and thenon to storage, while the oversized material is passed through a grindingmill and reduced to fines for recycling to the granulator. About twotons (1800 kg) of fine material per ton of product are required in therecycle stream.

Fumes from the granulator containing steam, ammonia and particulate arecollected by maintaining a negative pressure inside the granulator witha fan pulling the fumes into the rotary dryer to reduce the moisturecontent thereof. Air is drawn from the granulator at a rate of 20,000cubic feet per minute (cfm) at a temperature of 92.degree. C.(198.degree. F.) and at 100% relative humidity. This is roughlyequivalent of conveying 34,200 pounds per hour (lbs/hr) of water and 296pounds per minute (lbs/min) of dry air.

The air from the rotary dryer is conveyed to a dust cyclone, a baghousefilter, and then a scrubber. Air is drawn from the dryer at a rate of70,000 cfm at 45% relative humidity. The air leaving the dryer has a drybulb temperature of 93.degree. C. (200.degree. F.) and a wet bulbtemperature of 74.degree. C. (165.degree. F.). This is roughlyequivalent of conveying 56,100 lbs/hr water and 2,711 lbs/min of dryair. Air entering the scrubber is scrubbed with low pH water. The low pHwater collects ammonia vapor present in the fumes, as well as dustparticles.

Air is conveyed from the scrubber to a regenerative thermal oxidizer ata rate of 67,100 cfm at a temperature of (165.degree. F.) and at 100%relative humidity. Oxidized air is then drawn from the regenerativethermal oxidizer and is exhausted through a stack approximately onehundred feet tall at a temperature of 93.degree. C. (200.degree. F).

Dust-laden air is collected from the grinding mills and screens by a fanmaintaining negative pressure on the equipment. The air is pulledthrough a cyclone system that removes about 97% of the dust. From thecyclones, the air is passed back to the rotary granulator and the dustis added to the recycled fines. The resulting fertilizer is determinedto have an NPK value.

Other embodiments and uses of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. All references cited herein,including all U.S. and foreign patents and patent applications,including U.S. patent application Ser. Nos. 08/852,663, 09/735,768 and09/416,370, are specifically and entirely incorporated herein byreference. It is intended that the specification and examples beconsidered exemplary only, with the true scope and spirit of theinvention indicated by the following claims.

1. A method of treating an organic waste material to form a nutritionalcomposition for plants comprising: mixing said organic waste materialwith scrubber water to form a slurry capable of being pumped; pumpingsaid slurry to a reactor selected from the group consisting of apipe-cross reactor and a tubular reactor for reaction with a base andacid to form a melt; spraying said melt onto a recycling bed of fines ina granulator, and flashing off water contained in said melt as steam;rolling said melt onto fine particles in said granulator to formgranulated particles; further reacting the melt with ammonia in thegranulator to complete product formation reaction; drawing fumes fromsaid granulator; oxidizing said fumes to reduce any noxious odorassociated therewith; and drying said granulated particles in said dryerto reduce the moisture content thereof to form dried granulatedparticles comprising an enhanced plant nutrient value composition. 2.The method of claim 1 wherein the organic waste material comprisesrelatively low analysis organic waste material.
 3. The method of claim 1wherein the reactor is a pipe-cross reactor.
 4. The method of claim 1which does not exhaust significant amounts of noxious odors.
 5. Aprocess for preparing a composition that is capable of providingnutrition to plants from a waste material comprising: pumping a slurryform of the waste material through a pipe reactor for reaction with atleast one base or acid to form a high temperature melt; spraying themelt from the pipe reactor directly onto a recycling bed of fines in agranulator, and flashing off water contained in the melt as steam;rolling the melt onto particles in the granulator to form granulatedparticles; and drying the granulated particles to reduce the moisturecontent thereof to form dried granulated particles.
 6. The process ofclaim 5 wherein the pipe reactor is located within the granulator. 7.The process of claim 6 wherein the granulator is a rotating cylinder. 8.The process of claim 5 wherein the pipe reactor comprises two crosspipes.
 9. The process of claim 8 wherein two acids are introduced viathe two cross pipes.
 10. The process of claim 9 wherein the two acidsare sulfuric acid and phosphoric acid.
 11. The process of claim 5wherein the temperature is maintained at less than 149 degreescentigrade.
 12. The process of claim 5 further comprising adding waterto the waste material to form a slurry prior to pumping.
 13. A system ofexothermically mixing a pipe fed sludge slurry with one or more fluidreagents introduced by one or more cross pipes to produce a hightemperature mixture, wherein the temperature is controlled by a feedbacksystem that adjusts turbulence introduced by a protuberance.
 14. Thedevice of claim 13 wherein the protuberance is selected from the groupconsisting of a bump in the plumbing, at least two bumps in theplumbing, an orifice plate and two or more orifice plates.
 15. Thesystem of claim 13 wherein the turbulence is adjusted by at least oneaction selected from the group consisting of moving the protuberance,altering the penetration of the protuberance into the plumbing,switching of cross pipe reactors, adjusting the flow rate of the sludge,and adjusting the flow rate of one or more of the fluid reagents.